University of Wisconsin-Madison transportation-safety engineers are testing a system on a northern Wisconsin highway that could help reduce crashes at rural intersections across the country. While a vast system of limited-access interstate highways connects major cities around the United States, an even greater number of back roads and county and state highways enables drivers to travel efficiently from farm to farm, and town to town.

Yet, the eminently accessible nature of these rural roadways is also the very thing that makes them dangerous—particularly in places where two roads meet. “Intersection crashes account for 45 percent of all crashes, and 21 percent of fatal crashes,” says Madhav Chitturi, an assistant researcher in the University of Wisconsin-Madison Traffic Operations and Safety Laboratory, or TOPS Lab. Under the direction of David Noyce, a UW-Madison associate professor of civil and environmental engineering, the TOPS Lab provides the framework for a comprehensive traffic operations and safety research program at the university.

Motorists on a rural road often encounter a two-way stop at the road’s intersection with a primary road, at which point they must remain stopped for traffic from the left or right. “Up to 80 percent of all rural intersection right-angle crashes are due to the selection of an insufficient gap by a driver entering or crossing the primary traffic stream,” Chitturi says.

In 2005, more than 9,200 Americans died in intersection crashes, says Chitturi, and nearly half of those crashes occurred at rural intersections.

The Rural Intersection Crash Avoidance System components include sensors on the main road that determine the position, speed and lane of travel of approaching vehicles. Photo courtesy of Madhav Chitturi, UW-Madison Traffic Operations and Safety Laboratory.

Developed at the University of Minnesota Intelligent Vehicle Lab, the Rural Intersection Collision Avoidance System aims to avoid these crashes by giving real-time warnings about unsafe gaps to drivers crossing the primary traffic stream.

The system is comprised of three components: sensing, computation and electronic message signs. Sensors on the main road determine the position, speed and lane of travel for vehicles approaching the intersection. The computation system collects data from the sensor, computes vehicle trajectories, and assesses crash threats. This threat assessment yields three states in the system: inactive, which means there is no traffic threat; alert, which means there are conditions that require careful consideration; and warning, a situation in which drivers should avoid dangerous maneuvers. As determined by the computational system, the electronic message sign relays those relevant alerts and warnings to a driver waiting at an intersection.

In Wisconsin, a 2006 Wisconsin Department of Transportation-sponsored study identified six intersections with an unusually high number of right-angle crashes along a 95-mile stretch of U.S. Highway 53 from Barron County to Douglas County. “The crash rate at the intersection of U.S. 53 and Wisconsin Highway 77 was more than six times the expected crash rate for a similar intersection,” says Chitturi. “From 1998 to 2004 ,there were 30 crashes—five of which involved fatalities, and 15 of which involved injuries. Despite several safety improvements made by the Wisconsin Department of Transportation, the intersection continued to have severe crashes.

Working with researchers in the University of Minnesota Intelligent Vehicles Lab and the Wisconsin Department of Transportation, Chitturi and TOPS deputy director Todd Szymkowski implemented an experimental rural intersection collision avoidance system at the crash-prone intersection of U.S. 53 and Wisconsin Highway 77 in Minong.

The UW-Madison researchers implemented the system in Minong in April 2010. It is the second installation of the system in the United States, after Cannon Falls, Minnesota, in January 2010. “Improved safety at the Minong intersection will provide motivation for further deployments in Wisconsin and throughout the United States,” says Chitturi.

In recognition of the system’s potential for major safety improvements, the Intelligent Transportation Society of Wisconsin, a chapter of the Intelligent Transportation Society of America, awarded the crash avoidance project its 2010 ITS Project of the Year Award at its annual forum on Oct 26 in Brown Deer, Wisconsin.